A selective fire firearm can be fired in both semi-automatic and any number of automatic modes by means of a selector. Some selective fire weapons utilize burst fire mechanisms that limit the maximum or total number of shots fired when in this mode. The most common burst fire modes are two or three rounds per pull of the trigger.
Selective fire weapons, by definition, have a semi-automatic mode, where the weapon automatically reloads the chamber after each round is fired, but requires that the trigger be pulled again before firing the next round. This allows for rapid and (in theory) aimed fire along with conservation of ammunition. In some weapons, the selection is between different rates of automatic fire and/or varying burst limiters. The selection is often by a small rotating switch usually integral with the safety catch, but there have been other ways of choosing the mode of fire.
Some selective fire weapons offer a burst mode as the second option, where each pull of the trigger automatically fires a predetermined number of rounds (generally 3; sometimes 2 or 4), but won't fire any more until the trigger is pulled again. The current U.S. standard assault rifle, the M16A2, fires three rounds with each pull of the trigger when it is in burst mode. The M4A1 carbine variant of this rifle has the same fire selector. A common version of the Heckler & Koch MP5 submachine gun (widely used by SWAT teams and special operations military personnel) has the capability to fire 2, 3, or 4 round bursts, or to be fired fully-automatically. This is also the case of the French FAMAS or the Swiss SIG SG 550. Some automatic cannons have larger burst limiters to coincide with higher rates of fire.
The majority of selective fire weapons have a fully-automatic mode as the second option. With each pull of the trigger, the weapon continues to load and fire rounds until the trigger is released or the ammunition is depleted. The British L85A2; the American M16A1 of the Vietnam War; the ubiquitous Soviet-designed AKM; the Israeli Galil; some variants of the Belgian FN FAL; the Chinese QBZ-95; and the German G3 rifle are but a few examples of this type of selective fire weapon.
Selective fire weapons are regulated in the United States under the National Firearms Act of 1934; their new manufacture for the civilian market was prohibited by the Firearm Owners Protection Act of 1986.